In wireless communications, it is often desirable to be able to take advantage of directional communications in order to provide a higher quality of service than that available by using onmi-directional communications at the same power levels. This directionality provides greater gain in the desired direction causing fewer bit errors and the improved capability of acquiring a signal. For transmitting, all of the transmit power of a particular device may be focused toward the intended receiver. With respect to receiving signals, higher gain is directed on the source and very little gain is placed elsewhere. Beamforming using an adaptive antenna array is a method of realizing such a directional communication system.
An adaptive antenna array can provide higher gain in the direction required by digitally shifting the phases of the received signals from each antenna element (alternatively, the phase may be shifted using analog phase shifters as well). The logical solution to obtaining more gain and a narrower beam width is to increase the size and number of elements in the array. This poses a problem however, because the computational load to find sync on a signal with a large array increases exponentially as you increase the side length of the array. For example, a 4×4 element array may use 16 correlators to produce a correlation result for the received signal at each element of the array. These correlations could then be noncoherently summed and the peak of this correlation sum could then be used to find the sync position for the received signal. If a 100×100 element array were used, this would require 10,000 correlators running full time in order to find sync. At this size, the computational load may make using the array unpractical.
Accordingly, there is a need for a method for effectively using the gain and directionality of a large array by using the computations required by a small array. Further, there is a need for computationally simplifying the beamforming process for a large antenna array.
The techniques herein below extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned needs.